EVALUATION OF DEFORMATION PARAMETERS OF ORGANIC …

1. InTrODUCTIOnA characteristic element in the geological structurefound in Poland is the occurrence of deposits whichare a result of fluvial and lacustrine accumulation.These deposits include normally consolidated non-cohesive deposits in the form of sands, organic soilsand silts. Deposits of this type very often constitutesubsoil for road structures and large-scale objects.There has been considerable interest in Poland in thelast 20 years in static penetration methods such asCPTU, SCPTU and dilatometer testing (DMT).These three types of tests are crucial for the determi-nation of strength and deformation parameters in

organic soils and other normally consolidateddeposits. An obvious advantage of these tests is thepossibility to reduce to the minimum the number ofsamples for laboratory analyses. Problems with collec-tion of high quality samples from peats, soft silts andsands below water level are commonly known. Keyparameters for rational design of road embankmentsand large structures are soil stratigraphy and spatialvariability of constrained modulus. A description ofthe spatial variation of subsoil deformation may beobtained by constructing a model of subsoil rigiditybased on the established constrained modulus [8]. Inthe construction of the model of rigidity for soft soils,CPTU and SDMT results are very suitable, since they

EVALUATION OF DEFORMATION PARAMETERS OF ORGANIC SUBSOIL BY MEANS OF CPTU, DMT, SDMT

Zbigniew MŁYNAREK a*, Jędrzej WIERZBICKI b, Katarzyna STEFANIAK c

a Prof.; Poznań University of Life Sciences, Piątkowska 94, 61-691, Poznań, Poland

b Prof.; Institute of Geology, Adam Mickiewicz University, Maków Polnych 16, 61-606 Poznań, PolandE-mail address: [email protected]

c Dr.; Poznań University of Life Sciences, Piątkowska 94, 61-691, Poznań, Poland

Received: 30.10.2013; Revised: 30.11.2013; Accepted: 15.12.2013

A b s t r a c tThe paper presents a description of deformation parameters of subsoil composed of peat, mud and sand, which intended tobe the foundation for the reservoir with a diameter of 30 meters. Performed CPTU, DMT and SDMT tests, allowed to deter-mine the value of Go modulus and constrained modulus M. The paper also discusses interrelationships between mechani-cal parameters presented above. Using statistical methods the influence of factors on these relationships was examined. TheIDW method was used for determination of global rigidity subsoil model, used in the final conception in reservoir founda-tions.

S t r e s z c z e n i eW artykule przedstawiono opis cech wytrzymałościowych i deformacyjnych gruntów organicznych, pyłów i piasków, którestanowić mają podłoże zbiornika o 30 metrowej średnicy. Wykonane badania CPTU, DMT i SDMT, pozwoliły na określeniewartości początkowego modułu odkształcenia postaciowego Go oraz modułu ściśliwości M badanych gruntów. W pracyprzedstawiono zależności pomiędzy wspomnianymi parametrami oraz przedyskutowano wpływ różnych czynników na tezależności. Zaprezentowano również model sztywności podłoża, opracowany w oparciu o metodę IDW i wykonany na potrze-by analizy posadowienia zbiornika.

K e y w o r d s : Organic soil; In situ tests; Compressibility.

4/2013 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 51

A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T The Si les ian Univers i ty o f Technology No. 4/2013

Z . M ł y n a r e k , J . W i e r z b i c k i , K . S t e f a n i a k

provide a large number of measurements and a con-tinuous picture of changes in mechanical parametersof subsoil with depth. On the other hand, the inter-pretation of characteristics of CPTU and SDMT test-ing in organic soils and glacilacustrine deposits is stilldebatable, since a question arises whether relation-ships known from mineral soils may be adopted forthe prediction of soil type and constrained modulusof organic soils and other glacilacustrine deposits.

2. CHArACTErISTICS OF THE TEST-InG ArEA Tests were performed in two sites with a markedlydifferent genesis of subsoil. The selection of the loca-tions for CPTU and SDMT testing was based on theconcept to have subsoils significantly differing in thegenesis and lithology of the soil. Site 1 was character-ized by the presence of normally consolidateddeposits of delta accumulation, while in the other siteoverconsolidated glacifluvial deposits were found.The site with normally consolidated deposits is locat-ed in the delta of the Wisła river. Subsoil structure inthis site is determined by the accumulation and ero-sion processes, typical of delta areas. A characteristicfeature of organic layers is their relatively small thick-ness (approx. 1 m) and the fact that they are found at

different depths in the profile. The content of organ-ic matter in these soils ranges from 12 to 27%, whilebulk density ranges from 1.3 to 1.6 t/m3 and naturalwater content within the range from 54 to 130%. Overconsolidated soils were found in the valley of theupper course of the Wisła river, between Katowiceand Kraków (Site 2) [1]. Fluvial deposits accumulat-ed in this area were overconsolidated by migratingdune fields, active at the end of the Pleistocene andthe beginning of the Holocene. The overconsolida-tion of these soils was also affected by cyclic changesin ground water levels, characteristic of the Wisła val-ley. The sedimentation profile in that site is monoto-nous, composed of layers of medium sands and occa-sionally fine sands.Typical profiles in CPTU and DMT testing of soils inthe first site are presented in Fig. 1. The CPTU andDMT tests were typically spaced about 10m apart.Results of the tests made it possible to evaluatedeformation parameters of the subsoil. The CPT con-strained modulus, corresponding to the oedometermodulus MCPT, was determined according to themethodology proposed by Sanglerat [17] assuming acone coefficient α to be between 3 and 4. In case ofthe interpretation of DMT a standard procedureaccording to Marchetti (1980) was applied. Values of

52 A R C H I T E C T U R E C I V I L E N G I N E E R I N G E N V I R O N M E N T 4/2013

Figure 1.Typical CPTU and SDMT characteristics of soils in the Wisła delta (test site 1)

E VA L U AT I O N O F D E F O RMAT I ON PA R AME T E R S O F O RG AN I C S U B SO I L B Y M E ANS O F C P T U , DM T, S DMT

modulus G0 were determined based on the measure-ment of shear wave velocity, according to the assump-tions presented by Młynarek et al. [9]. Specific gravi-ty of soil as well as its mineral and grain size distribu-tion were determined on the basis of high qualitysamples.

3. CPTU AnD DMT CLASSIFICATIOnSYSTEMS FOr IDEnTIFICATIOn OFOrGAnIC SUBSOIL Applicability of commonly applied classificationcharts for DMT and CPTU testing and their use inthe identification of mineral soils found in Polandwas assessed in numerous analyses [10]. However,these investigations showed that the identification oforganic soils in typical CPTU systems is doubtful. Inthis paper the location of tested soils was analyzed inthe DMT diagram by Marchetti and Crapps [5] andCPTU diagrams by Robertson [15] and SCPT byRobertson et al. [16]. The location of non-cohesivesoils found in sites 1 and 2 in the CPTU and DMTclassification charts identifies very well the lithologyof the subsoil (Fig. 2). Differences in the interpreta-tion appear for the organic soils. Młynarek et al. [8],[9] showed that the DMT diagram very well identifiesthe structure of organic subsoil (Fig. 2a). In thisrespect the use of the CPTU diagram leads to anerroneous interpretation of results, since organicsoils are located in the zone allocated for silty claysand sensitive soils (Fig. 2b). This fact results from therecording of relatively high values of cone resistanceand low values of sleeve friction in the organic soils.Such a situation may be explained by the consider-able admixture of the sand fraction in these soils,characteristic of soils of fluvial accumulation. Muchbetter results are provided when the value of G0 istaken into consideration and the diagram byRobertson [16] is used (Fig. 2c). The application ofmodulus G0 in the construction of a CPTU classifica-tion chart for the determination of organic soil layersin the subsoil was also pointed to by Long [3].

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ca

b

c

Figure 2.Locations of tested soils on the DMT classification chart [5] (a) and CPTU classification chart [15] (b) and onthe SCPTU classification chart [16] (c)


4. rELATIOnSHIP BETWEEn CPTUAnD DMT FOr THE DETErMInATIOnOF COnSTrAInED MODULUS OF SUB-SOIL Modulus, which describe deformability or compress-ibility of subsoil, are determined based on laboratorytests or estimated from DMT and CPTU tests, usingcorrelations, e.g. [4], [6], [11]. Measurements of theseismic wave, performed in SCPTU and SDMT areused in the determination of the small strain shearmodulus G0. Thus, simultaneous CPTU, DMT andseismic tests make it possible to compare values ofboth modulus. An example of such an attempt is thecorrelation proposed by Marchetti et al. [7] for DMT,in which a relationship between a ratio of G0 to M,and the value of horizontal stress index KD is suggest-ed. In turn, high consistency between modulus G0

determined in SCPTU and SDMT was shown forpost-floatation deposits by Młynarek et al. [9]. Withinthe framework of the investigations connected withthis paper the applicability of these dependencies wasanalyzed for the assessment of the constrained mod-ulus of the tested soils. Fig. 3b shows that sands arevery well located in the graph by Marchetti et al. [7],which means that this dependence may be used forthe indirect determination of modulus G0 based onDMT results. The relationship for organic soils to acertain degree corresponds with a curve establishedfor clays, although at lower values of G0/M itapproaches the values characteristic of sands. Verysimilar results were obtained after replacement ofmodulus M determined from DMT, with the value ofthe modulus determined from CPTU (Fig. 3a). Thisstatement needs to be considered highly significant,since an analytical notation of the formula makes itpossible to determine modulus G0 on the basis ofmodulus M from CPTU and observations of changesin this modulus with depth. It is of interest to consider the relationship betweenmodulus G0 and M for the organic soils and to deter-mine how this dependence is determined. The analy-sis of the process of static penetration and thedilatometer test in organic soils conducted byMłynarek et al. [13] showed that there are severalfactors which affect the course of penetration charac-teristics and measured parameters in DMT and as aconsequence the determined constrained modulus.This analysis showed that the effect of these factorson both tests varies. In the hierarchy of factors, whoseeffect on cone resistance or values of measurement

for pressures p0 and p1 is most significant in organicsoils, the key positions are taken by overburdenstress, OCR and soil moisture content. Due to thecomplex preconsolidation processes of organic sub-soil at site 1, the effect of this factor on the depen-dence between modulus G0 and M was analyzed.Values of OCR for peat from different depositionlevels in the subsoil were determined on the basis ofoedometer laboratory tests and in situ methods [18].Based on this analysis preconsolidation stress σ’p wasdetermined and OCR was calculated according to thedefinition proposed by Casagrande OCR = σ’p/σ’v0.


Figure 3.A relationship between the factor of proportionality of mod-ulus G0/M from DMT (a) and CPTU (b) and the horizontalstress index KD

a

b


It results from Fig. 4 that the effect of OCR on therelationship between modulus G0 and M is statistical-ly significant and the correlation is described by ahigh regression coefficient.

In geotechnical practice different formulas are usedto estimate modulus G0 on the basis of CPTU results,thus a comparative analysis was conducted for sever-al formulas with values of the modulus provided bythe seismic test. Both in case of organic soils andsands a formula given by Rix and Stokoe [14] was

used for the calculation of G0 values on the basis ofCPTU results, whose applicability for mineral soilsfound in Poland was confirmed by Godlewski andSzczepański [2]. Modulus G0 from DMT was estimat-ed based on formulas given by Marchetti et al. [7]. Incase of the organic soils both the formula developedfor clays and that for sands were used. Moreover,relationships developed by the authors for CPTU andused are described by the formulas given below:

G0 = 49.97(MCPTUKD)-1.0 for sands (1)

G0 = 12.35(MCPTUOCR)0.13 for organic soils (2)

In Fig. 5 line C shows the most statistically significantrelationship between modulus G0 determined fromseismic testing as well as DMT and CPTU. It resultsfrom this Figure that the formula, which was devel-oped based on the author’s studies, makes it possibleto forecast modulus G0 with high accurancy, sincepoints defining the relationship between modulusestablished from both tests for organic soils are locat-ed on line C, while for non-cohesive soils along thisline. The other formulas are of little use for theassessment of this parameter in organic subsoil. It isof great practical importance to know this depen-dence, since DMT is a point test, while a continuouspicture of changes in modulus M and G0 in the sub-soil may be obtained from CPTU.

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Figure 4.A relationship between the results of SDMT and CPTU &laboratory tests for organic soils

Figure 5.A comparison of values of modulus G0 determined from the seismic test and calculated based on CPTU and DMT for organic soilsand sands

a b


Figure 6 presents a relationship between modulusdetermined from CPTU and DMT for non-cohesiveand organic soils. In case of non-cohesive soils it canbe observed high consistency of results from bothstudies. Absolute differences in values of modulus fororganic soils are similar to those for sands; however,taking into consideration relative differences (in rela-tion to the range of the modulus in these soils) itneeds to be stated that both methods yield signifi-cantly different results. The modulus from CPTU hasan almost constant value for organic soils (approx. 3 MPa), while the modulus from DMT changes with-in a range from 2 to 6 MPa).

5. APPLICATIOn OF CPTU AnD DMTrESULTS FOr THE COnSTrUCTIOnOF A MODEL OF SUBSOIL rIGIDITY For the evaluation of stability of a building structurewhich is to be founded on weak subsoil a crucial issueis to determine the model of rigidity for the subsoil,which will cooperate with the designed object.Having results of testing performed in w specific gridof points, it may be attempted to construct a spatialstructure of a model of subsoil rigidity (Fig. 10). Dueto the high number of measurements obtained inCPTU, statistical methods may be used for the con-struction of a model of subsoil rigidity [12]. For theconstruction of the model it can be used a modified

methodology of Inverse Distance Weighting calcula-tions. This method, by assuming specific parametersof the model, facilitates any change of significance ofthe weight of the distance and elliptical control of therange of interpolation and the number of data mea-sured and considered in the interpolation of traits,based on the formula (3).

where: v0 – interpolated value of parameter, �N(v0)� denotes the number of included observationsfrom the neighbourhood of v0, and weight wi. In caseof tested soils from the Wisła river delta the applica-tion of the above mentioned model made possible astatistically justified isolation of the range of soil lay-ers with reduced rigidity (Fig. 7). A crucial advantageof the constructed model is the fact that it facilitatesthe determination of the constrained modulus at anypoint of the subsoil zone which will cooperate withthe foundation. This element in turn is required forthe calculation of settlement of building structures ifadvanced rheological models are used in the calcula-tions and calculations for them are going to be con-ducted by the finite element method.

6. COnCLUSIOnSResults of conducted analyses make it possible to for-mulate several generalizations and conclusions:– factors, which affect parameters measured during

CPTU and DMT in organic soils differ from those,which have a crucial effect on CPTU and DMTcharacteristics in mineral soils. This fact limits theapplicability of empirical relationships for theassessment of constrained modulus of organic sub-soil, which were proposed by many authors formineral soils. On the other hand, analyses showedthat certain groups of factors such as σ’p (OCR)and the component of the state of stress, similarlyas in mineral soils have a statistically significanteffect on characteristics of the above mentionedtests in organic soils.

– The classification system proposed by Robertsonet al [16] for CPTU, in which modulus G0 is used,and the system by Marchetti and Craps [5] forDMT seem to be reliable systems for the identifi-


,)(

1

)(

10

0

0

=

==vN

ii

vN

iii

w

vwv (3)

Figure 6.A comparison between constrained modulus derived fromCPTU and DMT


cation of organic soils in subsoil. The use of thesesystems may be suitable for the identification ofsamples for laboratory analyses, and first of all forthe determination of the range of layers found inthe subsoil.

– Analyses showed that even from such complexsubsoil, as the subsoil composed of organic soils,local correlations between CPTU and DMT para-meters are described by a statistically significantcorrelation. Determined relationships facilitateassessment of modulus G0 and M from both tests.These dependencies are of particular value whenin the analyzed area both tests are going to be per-formed, since from the point assessment of modu-lus obtained from SDMT it is possible to go to acontinuous assessment of changes in these modu-lus with depth.

rEFErEnCES[1] Bzówka J.; Interaction of jet grounting columns with

subsoil (Współpraca kolumn wykonywanych technikąiniekcji strumieniowej z podłożem gruntowym).Silesian University of Technology Publ. (Wy -dawnictwo Politechniki Śląskiej), Gliwice, Poland,2009

[2] Godlewski T., Szczepański T.; (2011); Non-linear soilstiffness characteristic (G0) – methods of determina-tion, examples of application (Nieliniowa charakter-sytyka sztywności gruntu (G0) – metody oznaczaniai przykłady zastosowań). AGH Journal of Mining andGeoengineering. Iss.35, No.2, 2011; p.243-250

[3] Long M.; Design parameters from in situ tests in softground – recent developments. Geotechnical andGeophisical Site Characterization. Huang & Mayne(eds). Taylor & Francis Group, London, 2008; p.89-116

[4] Lunne T., Robertson P.K., Powell J.J.M.; ConePenetration Testing in geotechnical practice. Reprintby E & FN Spon, London, 1997

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Figure 7.The rigidity model of test site 1

c


[5] Marchetti S., Crapps D.K.; Flat Dilatometer Manual.Internal report of GPE Inc., 1981

[6] Marchetti S., Monaco P., Totani G. & Calabrese M.;The Flat Dilatometer Test (DMT) in soil investiga-tions. A Report by the ISSMGE Committee TC16,2001

[7] Marchetti D., Marchetti S., Monaco P.; Interrelationshipbetween small strain modulus G0 and operative mod-ulus. Prepared for IS-Tokyo 2009 – EarthquakeGeotechnical Engineering Conference, 2009

[8] Młynarek Z.; Evaluation of soil parameters by in-situtests for mapping. Architecture Civil EngineeringEnvironment. The Silesian University of TechnologyVol.1, 2008; p.75-98

[9] Młynarek Z., Gogolik S., Marchetti S., Marchetti D.(2006); Suitability of SDMT tetst to assess geotechni-cal parameters of post-flotation sediment. In Proc. of2nd Int. Flat Dilatometer Conference, 2006; p.148-153

[10] Młynarek Z., Tschuschke W., Wierzbicki J.; Soil classifi-cation by means of CPTU (Klasyfikacja gruntówpodłoża budowlanego metodą statycznego sondowa-nia). Proc. of XI Polish Conference on SoilsMechanics and Foundation Engineering, Gdańsk,1997; p.119-126

[11] Młynarek Z., Tschuschke W., Wierzbicki J.; Some geot-echnical parameters of structural soils, case of loess-like sediments in Pogórze Rzeszowskie, Poland(Wybrane parametry geotechniczne gruntów struktu-ralnych na przykładzie lessopodobnych gruntów zas-toiskowych Pogórza Rzeszowskiego). Roczniki ARw Poznaniu 2005, Melior. Inż. Środ., Vol.26, 2005;p.283-292

[12] Młynarek Z., Wierzbicki J., Wołyński W.; An approachto 3D subsoil model based on CPTU results. W:Geotechnical Engineering in Urban Environments. V. Cuellar et. al (red.) Vol.3. Millpress Rotterdam;ISBN 978 90 5966 055 7, Vol.7, 2007; p.1721-1726

[13] Młynarek Z., Wierzbicki J., Long M.; Factors affectingCPTU and DMT characteristics in organic soils. W:Geotechnical in Marintime Engineering. Proc. of the11th Baltic Sea Geotechnical Conference. Eds.: Z. Młynarek, Z. Sikora & E. Dembicki. Vol.1, 2008;p.407-417

[14] Rix G.J., Stoke K.H.; Correlation of initial tangentmodulus and cone resistance. Proc. of Int. Symp. OnCalibration Chamber Testing, 1992; p.351-362

[15] Robertson P.K.; Soil classification using the cone penetration test. Canadian Geotechnical Journal,Vol.27, No.1, 1990; p.151-158

[16] Robertson P.K., Sasitharan S., Cunning J.C., Segs D.C.(1995); Shear wawe velocity to evaluate flow liquefac-tion. Journal of Geo. Eng., ASCE, Vol.121, No.3,1995; p.262-273.

[17] Sanglerat G.; The penetrometer and soil exploration.Elsevier, Amsterdam, 1972

[18] Wierzbicki J., Młynarek Z.; Identification of overcon-soildation effect by means of in situ tests(Identyfikacja efektu prekonsolidacji podłoża meto-dami in situ). Inżynieria Morska i Geotechnika, No.4,2012; p.277-285


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